Fitting, ferrule, and ferrule manufacturing method

ABSTRACT

A fitting to be connected to a pipe includes: a first member; a second member coupled by screw coupling with the first member; and a ferrule placed in an accommodation space formed by an inner circumferential surface of the first member, an inner circumferential surface of the second member, and an outer circumferential surface of the pipe. The ferrule has a rising portion including a first end portion, a pressed portion located closer to a second end portion than the rising portion, and an intermediate portion including a portion where an inner diameter is greater than the first end portion and the second end portion, the intermediate portion connecting together the rising portion and the pressed portion. The first member has a first tapered inner circumferential surface, which is an inner circumferential surface having a tapered shape, to be in contact with the first end portion of the ferrule. The second member has a pressing portion for pressing at least a portion of the pressed portion of the ferrule. The accommodation space has a first clearance space for accommodating the ferrule therein and allowing the rising portion to rise so as to increase an angle of the rising portion with respect to the outer circumferential surface of the pipe.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is continuation of U.S. application Ser. No.14/418,525, filed Jan. 30, 2015, which is a U.S. National StageApplication of International Application No. PCT/JP2013/063906 filed May20, 2013, which claims priority from Japanese Patent Application No.2012-169271 filed Jul. 31, 2012. The entirety of all the above-listedapplications are incorporated herein by reference.

The present invention relates to a fitting for use in connection betweenpipes such as fluid pipes for passing fluids therethrough.

BACKGROUND ART

For connection between fluid pipes, a double ferrule-type fitting is afitting that provides a high sealing property with a small tighteningtorque (see PTL 1 and PTL 2).

FIGS. 1A to 1C are views illustrating a typical double ferrule-typefitting. Referring to FIG. 1A, a double ferrule-type fitting 90 includesa fitting body 91, a nut 92, a front ferrule 93, and a back ferrule 94.

The fitting body 91 and the nut 92 are coupled together by screwcoupling. As the screw coupling is tightened, the nut 92 pushes the backferrule 94 (point a in the figure) as shown in FIG. 1A. The back ferrule94, pushed by the nut 92, pushes the front ferrule 93 (point b in thefigure) while sliding under the front ferrule 93 as shown in FIG. 1B. Asthe back ferrule 94 slides under the front ferrule 93, the front ferrule93 has its tip bite into a pipe 95 along a tapered surface of thefitting body 91 while rotating to rise so as to raise the rear end(point c in the figure).

Then, as the front ferrule 93 rises, with point b serving as the pointof effort and point d as the fulcrum, as shown in FIG. 1C, a strongbiting force is generated at point c as the point of load, thusrealizing a good seal mechanism.

With such a double ferrule-type fitting 90, it is possible tosubstantially prevent a fluid leakage because of its high sealingproperty.

On the other hand, various single ferrule-type fittings have beenproposed in order to reduce the cost by reducing the number of parts andto facilitate the installation (see PTL 3 to PTL 5). A singleferrule-type fitting is a fitting having a single ferrule, and includesa fitting body, a nut, and a ferrule. The ferrule, being pushed by thenut as the screw coupling is tightened, has its tip bite into the pipealong a tapered surface of the fitting body, thus realizing a sealmechanism. Using a single ferrule placed between the fitting body andthe nut reduces the number of parts and also facilitates theinstallation.

These single ferrule-type fittings obtain a force for making the tip ofthe ferrule bite into the pipe in the radially inward direction from theforce of the nut pushing the ferrule in the axial direction. The shapeof the single ferrule is devised so as to convert the direction of forcefrom the axial direction to the radially inward direction.

However, as opposed to a double ferrule-type fitting, where as the backferrule 94 slides under the front ferrule 93, the front ferrule 93rises, with point b serving as the point of effort and point d as thefulcrum, a single ferrule-type fitting changes the direction of force bythe shape of the single ferrule, and it is therefore not possible toefficiently generate a force in the radially inward direction generallyat the tip of the pipe.

PTL 6 provides various discussions on the characteristics of singleferrule-type fittings.

CITATION LIST Patent Literature

[PTL 1]

Japanese Translation of PCT Application No. 2003-529032

[PTL 2]

Japanese Translation of PCT Application No. 2009-523967

[PTL 3]

Japanese Translation of PCT Application No. 2010-509548 (FIGS. 1A to 1D,4A, 4B, 6A to 6C, 7, 8, 9, etc.)

[PTL 4]

Japanese Translation of PCT Application No. 2007-502940 (FIGS. 7, 7A, 8,13, 13A, 14, etc.)

[PTL 5]

Japanese Translation of PCT Application No. 2009-522525 (FIGS. 13, 14)

[PTL 6]

Japanese Patent Application Laid-open No. 2005-246967 (Paragraphs 0011to 0021, etc.)

SUMMARY OF INVENTION Technical Problem

As discussed above, a double ferrule-type fitting is capable ofefficiently obtaining a force for making the tip of the ferrule biteinto the pipe but has a larger number of parts, whereas a singleferrule-type fitting has a smaller number of parts but is not capable ofefficiently obtaining a force for making the tip of the ferrule biteinto the pipe. Thus, a double ferrule-type fitting and a singleferrule-type fitting both have advantages and disadvantages.

An object of the present invention is to provide a technique with whicha force for driving the tip of the ferrule to bite into the pipe can beefficiently generated with a small number of parts.

Solution to Problem

A fitting according to one embodiment of the present invention is afitting to be connected to a pipe, the fitting including: a first memberhaving a through hole for receiving the pipe; a second member having athrough hole for receiving the pipe, the second member being coupled byscrew coupling with the first member, with a central axis of the throughhole being aligned with a central axis of the through hole of the firstmember; and a ferrule having a through hole extending from a first endportion of the ferrule to a second end portion of the ferrule forreceiving the pipe, the ferrule including a portion having a greaterinner diameter than the first end portion and the second end portionbetween the first end portion and the second end portion, and theferrule being placed in an accommodation space formed by an innercircumferential surface of the first member, an inner circumferentialsurface of the second member and an outer circumferential surface of thepipe, with a central axis of the through hole being aligned with thecentral axes of the first member and the second member, wherein: theferrule has a rising portion including the first end portion, a pressedportion located closer to the second end portion than the risingportion, and an intermediate portion including a portion therein wherean inner diameter is greater than the first end portion and the secondend portion, the intermediate portion connecting together the risingportion and the pressed portion; the first member has a first taperedinner circumferential surface, which is an inner circumferential surfacehaving a tapered shape, to be in contact with the first end portion ofthe ferrule; the second member has a pressing portion for pressing atleast a portion of the pressed portion of the ferrule; the accommodationspace has a first clearance space for accommodating the ferrule thereinand allowing the rising portion to rise so as to increase an angle ofthe rising portion with respect to the outer circumferential surface ofthe pipe; and as the screw coupling between the first member and thesecond member is tightened, the rising portion of the ferrule rises torotate, with an outer circumference of the first end portion serving asa fulcrum and an inner circumference of the first end portion serving asa point of load, thereby implementing a drive to bite into an outercircumference of the pipe.

A ferrule according to one embodiment of the present invention is aferrule for use in a fitting to be connected to a pipe, the fittingincluding: a first member having a through hole for receiving the pipe;and a second member having a through hole for receiving the pipe, thesecond member being coupled by screw coupling with the first member,with a central axis of the through hole being aligned with a centralaxis of the through hole of the first member, the ferrule including: athrough hole penetrating from a first end portion of the ferrule to asecond end portion of the ferrule for receiving the pipe, a portionhaving a greater inner diameter than the first end portion and thesecond end portion being provided between the first end portion and thesecond end portion; a rising portion including the first end portion; apressed portion located closer to the second end portion than the risingportion; and an intermediate portion including a portion therein wherean inner diameter is greater than the first end portion and the secondend portion, the intermediate portion connecting together the risingportion and the pressed portion, wherein: the ferrule is placed in anaccommodation space, with a central axis of the through hole beingaligned with central axes of the first member and the second member, theaccommodation space being formed by an inner circumferential surface ofthe first member having a first tapered inner circumferential surface,which is an inner circumferential surface having a tapered shape, to bein contact with the first end portion of the ferrule, an innercircumferential surface of the second member having a pressing portionfor pressing at least a portion of the pressed portion of the ferrule,and an outer circumferential surface of the pipe, and the accommodationspace having a first clearance space for accommodating the ferruletherein and allowing the rising portion to rise so as to increase anangle of the rising portion with respect to the outer circumferentialsurface of the pipe; and as the screw coupling between the first memberand the second member is tightened, the rising portion of the ferrulerises to rotate, with an outer circumference of the first end portionserving as a fulcrum and an inner circumference of the first end portionserving as a point of load, thereby implementing a drive to bite into anouter circumference of the pipe.

A ferrule manufacturing method according to one embodiment of thepresent invention is a ferrule manufacturing method for manufacturing aferrule for use in a fitting, the fitting including: a first memberhaving a through hole for receiving the pipe; a second member having athrough hole for receiving the pipe, the second member being coupled byscrew coupling with the first member, with a central axis of the throughhole being aligned with a central axis of the through hole of the firstmember; and a ferrule having a through hole extending from a first endportion of the ferrule to a second end portion of the ferrule forreceiving the pipe, the ferrule including a portion having a greaterinner diameter than the first end portion and the second end portionbetween the first end portion and the second end portion, and theferrule being placed in an accommodation space formed by an innercircumferential surface of the first member, an inner circumferentialsurface of the second member and an outer circumferential surface of thepipe, with a central axis of the through hole being aligned with thecentral axes of the first member and the second member, wherein: theferrule has a rising portion including the first end portion, a pressedportion located closer to the second end portion than the risingportion, and an intermediate portion including a portion therein wherean inner diameter is greater than the first end portion and the secondend portion, the intermediate portion connecting together the risingportion and the pressed portion; the first member has a first taperedinner circumferential surface, which is an inner circumferential surfacehaving a tapered shape, to be in contact with the first end portion ofthe ferrule; the second member has a pressing portion for pressing atleast a portion of the pressed portion of the ferrule; the accommodationspace has a first clearance space for accommodating the ferrule thereinand allowing the rising portion to rise so as to increase an angle ofthe rising portion with respect to the outer circumferential surface ofthe pipe; and as the screw coupling between the first member and thesecond member is tightened, the rising portion of the ferrule rises torotate, with an outer circumference of the first end portion serving asa fulcrum and an inner circumference of the first end portion serving asa point of load, thereby implementing a drive to bite into an outercircumference of the pipe, the method including: severing a long pipemember to produce a short pipe member having a predetermined length, theshort pipe member having a uniform outer diameter and a uniform innerdiameter between opposite ends thereof to be the first end portion andthe second end portion; and machining the short pipe member to form therising portion, the intermediate portion and the pressed portion betweenthe first end portion and the second end portion, which both have suchan inner diameter that the pipe can be accommodated therein.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1A is a view illustrating a typical double ferrule-type fitting.

FIG. 1B is a view illustrating, along with FIG. 1A, a typical doubleferrule-type fitting.

FIG. 1C is a view illustrating, along with FIGS. 1A and 1B, a typicaldouble ferrule-type fitting.

FIG. 2 is a cross-sectional view of a fitting according to the presentembodiment.

FIG. 3 is a view illustrating the motion and function of various partswhen the fitting is mounted on a pipe.

FIG. 4 is a view illustrating the principle by which the ferrule isdriven to bite into the pipe.

FIG. 5 is a view illustrating the principle by which the ferrule isdriven to bite into the pipe.

FIG. 6 is a graph obtained by measuring changes in the relative positionof the front end portion of the ferrule with respect to the pipe whenthe front end portion of the ferrule is driven to bite into the outercircumference of the pipe.

FIG. 7 is a view illustrating various machining methods formanufacturing a ferrule.

FIG. 8 is a view illustrating another machining method for manufacturinga ferrule.

FIG. 9 is a view illustrating a variation of the fitting according tothe present embodiment.

FIG. 10 is a view illustrating a fitting according to another variation.

FIG. 11 is a view illustrating a fitting according to still anothervariation.

FIG. 12 is a view illustrating a fitting according to still anothervariation.

FIG. 13 is a view illustrating a fitting according to still anothervariation.

FIG. 14A is a view illustrating a fitting according to still anothervariation.

FIG. 14B is a view illustrating, along with FIG. 14A, a fittingaccording to a variation.

DESCRIPTION OF EMBODIMENTS

An example embodiment of the present invention will be described belowwith reference to the drawings.

FIG. 2 is a cross-sectional view of a fitting according to the presentembodiment. Referring to FIG. 2, a fitting 10 includes a fitting body11, a nut 12, and a ferrule 13. A fitting is used connected to a pipefor purposes of connecting together pipes for passing a fluidtherethrough.

The fitting body 11 and the nut 12 are coupled together by screwcoupling, which can be tightened and loosened. The fitting body 11, thenut 12 and the ferrule 13 have a through hole receiving the pipe 95. Thefitting 10 receives the pipe 95 through the nut 12, the ferrule 13 andthe fitting body 11 in this order so that the ferrule 13 is accommodatedin the accommodation space formed by the inner circumferential surfaceof the fitting body 11, the inner circumferential surface of the nut 12and the outer circumferential surface of the pipe 95, and is connectedto the pipe 95 as the screw coupling between the fitting body 11 and thenut 12 is tightened.

The ferrule 13 includes, between a front end portion (first end portion)13 a and a rear end portion (second end portion) 13 b, a rising portion13 c, an intermediate portion 13 e and a pressed portion 13 d. Herein,it is assumed that the front side is defined as the side of the fittingbody 11, and the rear side as the side of the nut 12.

There is an area where the inner diameter is larger than the front endportion 13 a and the rear end portion 13 b between the front end portion13 a and the rear end portion 13 b of the ferrule. The rising portion 13c is an area, including the front end portion 13 a, where the innerdiameter and the outer diameter increase gradually toward the rear side.The pressed portion 13 d is an area, including the rear end portion 13b, where the inner diameter and the outer diameter decrease graduallytoward the rear side. The intermediate portion 13 e is an area betweenthe rising portion 13 c and the pressed portion 13 d, and includes aportion of the largest inner diameter.

The fitting body 11 has a tapered inner circumferential surface 11 a,which is an inner circumferential surface having a tapered shape, to bein contact with the front end portion 13 a of the ferrule 13. Thetapered inner circumferential surface 11 a and the outer circumferentialsurface of the rising portion 13 c of the ferrule 13 form apredetermined angle β along a plane that includes the central axis.

The nut 12 has a pressing portion 12 a for pressing at least a portionof the pressed portion 13 d of the ferrule 13.

The pressing portion 12 a has a tapered inner circumferential surface,which is an inner circumferential surface having a tapered shape, to bein contact with the rear end portion 13 b of the ferrule 13. The taperedinner circumferential surface and the pressed portion 13 d of theferrule 13 form a predetermined angle α along a plane that includes thecentral axis. Note that α and β may be set to appropriate values basedon the set values of various parameters such as the thickness of theferrule 13, the length of the intermediate portion 13 e, the shape ofthe pressed portion 13 d, and the shape of the pressing portion 12 a ofthe nut 12.

When the fitting body 11 and the nut 12 are in a finger-tight state, theaccommodation space has a clearance space 15 capable of accommodatingthe ferrule 13 therein, and further allowing the rising portion 13 c torise so as to increase the outer diameter of the intermediate portion 13e and increase the angle formed with respect to the outercircumferential surface of the pipe 95 (decrease the angle β). Thefinger-tight state is a state where the screw coupling between thefitting body 11 and the ferrule 13 has been tightened to such a degreethat the fitting body 11 and the ferrule 13 are in contact with eachother and the ferrule 13 and the nut 12 are in contact with each other,but there is no deformation of the ferrule 11.

Note that as an example, the present embodiment is directed to anexample where the clearance space 15 has two spaces: a first clearancespace 15 a capable of allowing the rising portion 13 c to rise so as toincrease the angle formed with respect to the outer circumferentialsurface of the pipe 95; and a second clearance space 15 b for increasingthe outer diameter of the intermediate portion 13 e for allowing therising portion 13 c to rise. The first clearance space 15 a is a spacelocated on the outer side (the upper side in FIG. 2) of the risingportion 13 c, and the second clearance space 15 b is a space located onthe outer side (the upper side in FIG. 2) of the intermediate portion 13e. However, the present invention is not limited to this example. Inother examples, the fitting may include the first clearance space 15 abut no second clearance space 15 b, and the rising portion 13 c cannevertheless rise because of the provision of the first clearance space15 a.

By aligning together the central axes of the nut 12, the ferrule 13 andthe fitting body 11, then receiving the pipe 95 through the nut 12, theferrule 13 and the fitting body 11 in this order, and then tighteningthe screw coupling between the fitting body 11 and the nut 12 from thefinger-tight state with a predetermined tightening torque by apredetermined amount of tightening, the front end portion 13 a of theferrule 13 bites into the pipe 95 to form a seal, thereby connecting thefitting 10 to the pipe 95.

According to the present embodiment, since the intermediate portion 13 eof the ferrule 13 has a portion of a large inner circumference, therising portion 13 c rises while the intermediate portion 13 e bulgesoutwardly, with the ferrule 13, being pushed by the nut 12, remainingabutted against the fitting body 11. When the rising portion 13 c of theferrule 13 rises, the outer circumference of the front end portion 13 acontacts the tapered inner circumferential surface 11 a of the fittingbody 11 so that the movement thereof is restricted. Therefore, a forcefor driving the inner circumferential portion of the front end portion13 a in contact with the pipe 95 to bite into the pipe 95 is efficientlygenerated, and the fitting 10 is connected to the pipe 95 in such astate that a sealing property can be obtained.

Now, the action and function of various parts when the fitting 10 ismounted on the pipe 95 will be further described. FIG. 3 is a viewillustrating the motion and function of various parts when the fittingis mounted on a pipe.

Referring to FIG. 3, as the screw coupling between the fitting body 11and the nut 12 is tightened, the pressing portion 12 a of the nut 12presses forward the pressed portion 13 d of the ferrule 13 by the forceF1 generated in the axial direction. The ferrule 13, with its pressedportion 13 d pressed, accordingly pushes forward the fitting body 11 infront of the ferrule 13. Then, as its reaction, the fitting body 11pushes rearward the ferrule 13.

The ferrule 13, with its front end portion 13 a pushed rearward and itsrear end portion 13 b pushed forward, deforms so that the front endportion 13 a and the rear end portion 13 b come closer to each otherwith the inner diameter and the outer diameter of the intermediateportion 13 e increasing due to the force F2 deriving from the force F1.Then, the rising portion 13 c rises so as to increase the angle formedwith respect to the outer circumference of the pipe 95 until the angleof the outer circumferential surface thereof coincides with the angle ofthe tapered inner circumferential surface 11 a of the fitting body 11.

As the rising portion 13 c rises, the front end portion 13 a is drivenso that the outer circumferential portion thereof in contact with thetapered inner circumferential surface 11 a of the fitting body 11 isrestricted by the tapered inner circumferential surface 11 a, and theinner circumferential portion thereof in contact with the pipe 95 bitesinto the pipe. That is, the ferrule 13 is driven to bite into the pipe95 with a strong force based on the principle of leverage, with theouter circumferential portion of the front end portion 13 a of theferrule 13 serving as the fulcrum and the inner circumferential portionthereof as the point of load.

Since the deformed ferrule 13 remains to have some elastic force urgingit to return to the original shape, the ferrule 13 and the fitting body11 push each other while the ferrule 13 and the nut 12 push each other.As a result, it is possible to suppress the loosening of the fitting 10off the pipe 95 due to vibrations, etc. Since the elastic deformation ofthe ferrule 13 is such that the elastic force is lost when it returns tothe finger-tight state, the nut 12 and the ferrule 13 are prevented fromjumping out due to an elastic force when the fitting 10 is removed.

Now, the principle by which the ferrule 13 is driven to bite into thepipe 95 in the present embodiment will be described. FIGS. 4 and 5 areviews illustrating the principle by which the ferrule is driven to biteinto the pipe.

As shown in FIG. 4, the ferrule 13 of the present embodiment, as seenalong a cross section that passes through the central axis, can beconsidered as a structure in which a member 13 c′ modeling the risingportion 13 c and a member 13 d′ modeling the pressed portion 13 d areconnected together at a connection point 13 e′ at one end thereof in thelongitudinal direction, and in which the member 13 c′ and the member 13d′ are further connected together at the midpoint thereof by an elasticbody 13 f′. In the absence of an external force on this structure, themember 13 c′ and the member 13 d′ remain at a predetermined angle due tothe elastic force of the elastic body 13 f′.

As the movement of a tip 13 a′ of the member 13 c′ toward the left sideis restricted by the fitting body 11, and the force F1 is applied in theleftward direction in the figure on the member 13 d′, the force F2 isderived which shrinks the elastic body 13 f′ and pushes the connectionpoint 13 e′ upward. As a result, a rotational motion occurs at the tip13 a′ of the member 13 c′.

Referring to an enlarged view in the vicinity of a tip 13 h′ shown inFIG. 5, with the entire member 13 c′ pressed against the pipe 95 and thefitting body 11, a rotational motion occurs at the tip 13 a′ of themember 13 c′, thereby rotating the point of load 13 h′ about the fulcrum13 g′ as the center, and driving the point of load 13 h′ so as to biteinto the pipe 95.

FIG. 6 is a graph obtained by measuring changes in the relative positionof the front end portion of the ferrule with respect to the pipe whenthe front end portion of the ferrule is driven to bite into the outercircumference of the pipe. A plurality of graphs indicated by solidlines in FIG. 6 represent a plurality of measurements obtained bymeasuring, with different parameter values, changes in the position ofthe front end portion 13 a when the front end portion 13 a of theferrule 13 is driven to bite into the outer circumference the pipe 95.What is indicated by a broken line in FIG. 6 represents a referenceexample showing changes in the position of the front end portion of thefront ferrule 93 in the double ferrule-type fitting 90 shown in FIGS. 1Ato 1C.

In FIG. 6, the horizontal axis represents the relative position in theaxial direction, and the vertical axis represents the relativedisplacement in the depth direction. For the horizontal axis and thevertical axis, the relative position in the finger-tight state is usedas the origin. In the axial direction, the value increases in thenegative direction as it moves forward. On the vertical axis, the valueincreases in the negative direction as the bite increases.

As can be seen from FIG. 6, when the screw coupling is tightened with apredetermined torque from the finger-tight state, the front end portion13 a of the ferrule 13 primarily moves in the axial direction withrespect to the pipe 95 in the initial stage. Past a certain point,however, the inner circumference of the front end portion 13 a of theferrule 13 engages with the outer circumference of the pipe 95, therebytransitioning to another stage where the front end portion 13 aprimarily moves in the biting direction based on the principle ofleverage occurring due to the rise of the rising portion 13 c. Thispoint of transition is the grip point in the figure. In the stage wherethe front end portion 13 a moves primarily in the biting direction, thefront end portion 13 a rather moves backwards as seen in the axialdirection. Upon completion of the rise of the rising portion 13 c, thefront end portion 13 a transitions into a stage where the front endportion 13 a again moves primarily forward. Thus, when the risingportion 13 c rises, the principle of leverage acts, with the outercircumference of the front end portion 13 a serving as the fulcrum andthe inner circumference of the front end portion 13 a as the point ofload, so that in at least a portion of the stage when the screw couplingis tightened, a phenomenon occurs where the inner circumference of thefront end portion 13 a bites into the outer circumference of the pipe 95while moving back in the opposite axial direction to the force by whichthe nut 12 pushes the ferrule 13 in the axial direction.

As the front end portion 13 a of the ferrule 13 is driven to bite asdescribed above, the ferrule 13 bites into the pipe 95 with a strongforce, thereby providing a sealing property. As the front end portion 13a of the ferrule 13 is driven to bite while once moving back in theopposite direction, the ferrule and the pipe 95 are desirably sealedtogether, thereby providing a strong sealing property. As can be seenfrom FIG. 6, with the single ferrule-type fittings (the presentembodiment) indicated by solid lines, the front end portion 13 a of theferrule 13 bites into the pipe 95 to a depth comparable to that for thedouble ferrule-type fitting indicated by a broken line.

Note that in the present embodiment, when the screw coupling between thefitting body 11 and the nut 12 is in the finger-tight state, the outercircumferential surface of the rising portion 13 c of the ferrule 13forms a predetermined angle β with respect to the tapered innercircumferential surface 11 a of the fitting body 11 along a crosssection that includes the central axis, as shown in FIG. 2. Thus, in thepresent embodiment, by allowing the rising portion 13 c to rise by theappropriate angle β, there is obtained a drive with an appropriateamount of bite, thus obtaining a desirable seal between the front endportion 13 a of the ferrule 13 and the pipe 95.

In the present embodiment, the pressing portion 12 a of the nut 12 has atapered inner circumferential surface, which is an inner circumferentialsurface having a tapered shape, to be in contact with the rear endportion 13 b of the ferrule 13, as shown in FIG. 2. Then, the outercircumferential surface of the pressed portion 13 d of the ferrule 13forms a predetermined angle α with respect to the tapered innercircumferential surface of the nut 12 along a cross section thatincludes the central axis. In the present embodiment, when the pressedportion 13 d is pressed by the pressing portion 12 a, the pressedportion 13 d rises so as to conform to the tapered inner circumferentialsurface of the pressing portion 12 a as the intermediate portion 13 eexpands outwardly. In this process, the rear end portion 13 b of theferrule 13 is driven so as to tighten the pipe 95. Then, in the presentembodiment, by allowing the pressed portion 13 d to rise by anappropriate angle β, there is obtained a drive with an appropriateamount of tightening, thereby allowing the rear end portion 13 b of theferrule 13 to desirably hold the pipe 95.

In the present embodiment, the ceiling surface of the accommodationspace formed by the inner circumferential surface of the fitting body11, the inner circumferential surface of the nut 12 and the outercircumferential surface of the pipe 95 may come into contact with theintermediate portion 13 e whose outer diameter has been increased withthe rising portion 13 c of the ferrule 13 having risen by the angle β.This can be realized by designing in advance so that the intervalbetween the apex present along the intermediate portion 13 e of theferrule 13 and the ceiling surface of the accommodation space is equalto a predetermined distance in the finger-tight state. Then, as therising portion 13 c rises by an appropriate angle β to achieve a statewhere a desirable seal is obtained between the ferrule 13 and the pipe95, the apex of the ferrule 13 is in contact with the ceiling surface ofthe accommodation space, thereby reinforcing the ferrule 13, making itpossible to maintain a desirable sealing property. Note that the ceilingsurface of the accommodation space may be formed by either the fittingbody 11 or the nut 12. In the present invention, it is not necessarythat the apex of the ferrule 13 is in contact with the ceiling surfaceof the accommodation space, and the apex of the ferrule 13 may be not incontact with the ceiling surface of the accommodation space.

With the ferrule 13 of the present embodiment, there is no particularlimitation on the thicknesses of the front end portion 13 a, the rearend portion 13 b, the rising portion 13 c, the pressed portion 13 d andthe intermediate portion 13 e. There is also no particular limitation onthe lengths of the rising portion 13 c, the intermediate portion 13 eand the pressed portion 13 d.

Note however that it is preferred that the thickness of the front endportion 13 a of the ferrule 13 is less than the length of the risingportion 13 c. If the length of the rising portion 13 c of the ferrule 13is greater than the thickness of the front end portion 13 a thereof, asthe rising portion 13 c rises, the movement of the front end portion 13a is restricted with the outer circumference thereof being in contactwith the tapered inner circumferential surface 11 a, and as the innercircumferential portion in contact with the pipe 95 is driven to biteinto the pipe 95, the inner circumference is driven to bite into thepipe 95 with a strong force based on the principle of leverage, with theouter circumference of the front end portion 13 a serving as thefulcrum, and the inner circumference thereof as the point of load.

Conversely, the thickness of the front end portion 13 a of the ferrule13 may be greater than the length of the rising portion 13 c. In thiscase, only by slightly increasing the outer diameter of the intermediateportion 13 e, the front end portion 13 a of the ferrule 13 can be drivento bite with an amount of bite greater than that.

In the present embodiment, the outer circumference of the front endportion 13 a of the ferrule 13 may be R-chamfered as shown in FIGS. 2and 3. Since the outer circumference of the front end portion 13 a isR-chamfered, when the rising portion 13 c rises, the outer circumferenceof the front end portion 13 a pressed against the fitting body 11 slidesagainst the tapered inner circumferential surface 11 a of the fittingbody 11, and the inner circumference of the front end portion 13 a isunlikely to slip on the pipe 95 so that it can be desirably driven tobite.

An example of a method for manufacturing the ferrule 13 of the fitting10 according to the present embodiment will now be described.

FIG. 7 is a view illustrating various machining methods formanufacturing a ferrule. FIG. 7 illustrates Machining Methods 1 to 4,including a cutting process.

In Machining Method 1, the ferrule 13 is produced only by a cuttingprocess. The ferrule 13 of a desired shape and size is produced from aworkpiece of a predetermined material by a cutting process. Since theslope of the rising portion 13 c including the front end portion 13 a onthe right side of the figure and the slope of the pressed portion 13 dincluding the rear end portion 13 b on the left side of the figure areboth formed by a cutting process, the cutting of the innercircumferential surface of the intermediate portion 13 e will be of aslightly high degree of difficulty.

In Machining Method 2, the ferrule 13 is produced by a cutting processand a pressing process.

First, a cutting process is performed to produce an intermediate member22. The slope of the rising portion 13 c on the front side (the rightside in the figure) is formed by a cutting process. The slope of thepressed portion 13 d in the rear end portion 13 b is not formed by acutting process, and the inner diameter and the outer diameter are setto be constant from the intermediate portion 13 e to the rear endportion 13 b.

Next, a pressing process is performed. The slope of the pressed portion13 d is formed by narrowing the vicinity of the rear end portion 13 bthrough a pressing process using a die of a predetermined shape.

In Machining Method 2, since the rear end portion 13 b of theintermediate member 22 produced at the cutting process stage has thesame inner diameter as the intermediate portion 13 e, the degree ofdifficulty of the cutting process is lower than Machining Method 1.

Machining Method 3 also produces the ferrule 13 by a cutting process anda pressing process.

First, a cutting process is performed to produce an intermediate member23. The slope of the pressed portion 13 d on the rear side is formed bya cutting process. The slope of the rising portion 13 c in the front endportion 13 a is not formed by a cutting process, and the inner diameteris set to be constant from the intermediate portion 13 e to the frontend portion 13 a. The outer diameter is also generally constant from theintermediate portion 13 e to the front end portion 13 a, but the outercircumference of the front end portion 13 a is R-chamfered.

Next, a pressing process is performed. The slope of the rising portion13 c is formed by narrowing the vicinity of the front end portion 13 athrough a pressing process using a die of a predetermined shape.

In Machining Method 3, since the front end portion 13 a of theintermediate member 23 produced at the cutting process stage has thesame inner diameter as the intermediate portion 13 e, the degree ofdifficulty of the cutting process is lower than Machining Method 1.

Machining Method 4 also produces the ferrule 13 by a cutting process anda pressing process.

First, a cutting process is performed to produce an intermediate member24. The slope of the pressed portion 13 d and the slope of the risingportion 13 c are not formed by a cutting process. The inner diameter isset to be constant from the front end portion 13 a to the rear endportion 13 b via the intermediate portion 13 e. The outer diameter isalso generally constant from the front end portion 13 a to the rear endportion 13 b, but the outer circumference of the front end portion 13 ais R-chamfered.

Next, a pressing process is performed. The slope of the rising portion13 c and the slope of the pressed portion 13 d are formed by narrowingthe vicinity of the front end portion 13 a and narrowing the vicinity ofthe rear end portion 13 b through a pressing process using a die of apredetermined shape.

In Machining Method 4, since the intermediate member 24 produced at thecutting process stage has the same inner diameter from the front endportion 13 a to the rear end portion 13 b, the degree of difficulty ofthe cutting process is lower than Machining Method 1. In this example,since the intermediate member 24 has a uniform inner diameter and auniform outer diameter from the front end portion 13 a to the rear endportion 13 b, the a cutting process step can be shortened by severing acommercially-available pipe material (long pipe member) and using it inthe cutting process.

FIG. 8 is a view illustrating another machining method for manufacturinga ferrule. FIG. 8 illustrates a machining method using a pressingprocess.

FIG. 8A shows a workpiece 31 for use in the pressing process. As anexample, the workpiece 31 is obtained by severing acommercially-available pipe material into a predetermined length.

FIG. 8B shows a state where the workpiece 31 has been set in a diesystem including dies 32 to 34. The die 33 has a portion where the innercircumferential surface thereof is narrowed into a tapered shape inward(rightward in the figure) from the insertion opening, through which theworkpiece 31 is inserted. The die 32 also has a portion where the innercircumferential surface thereof is narrowed into a tapered shape inward(leftward in the figure) from the insertion opening, through which theworkpiece 31 is inserted. The die 34, which is inserted through thethrough hole of the workpiece 31, has a tapered portion, where the outerdiameter gradually decreases, on the front side (on the right side inthe figure) of the cylindrical portion of a uniform outer diameter.

As shown in FIG. 8C, a pressing process is performed so as to sandwichthe workpiece 31 from the front side and the rear side by the die 33 andthe die 32 with the die 34 inserted through the inner circumference ofthe workpiece 31, thereby producing an intermediate member 35. Therising portion 13 c of the ferrule 13 is formed by the portion of thedie 33 where the inner circumferential surface has a tapered shape andthe tapered portion of the die 34. The prototype portion of the pressedportion 13 d of the ferrule 13 is formed by the portion of the die 32where the inner circumferential surface has a tapered shape and thecylindrical portion of the die 34 having a uniform outer diameter. Notehowever that at this stage, the prototype portion of the rear endportion 13 b has a greater inner diameter than the inner diameter of thefinal rear end portion 13 b.

Then, as shown in FIG. 8D, a pressing process is performed by a diesystem in which the dies 32 and 34 of FIG. 8C are replaced by dies 36and 37. The die 37 inserted through the through hole of the intermediatemember 35 has a portion to be inserted that is a cylinder whose outerdiameter coincides with the inner diameter of the final rear end portion13 b. The insertion opening of the die 36, through which theintermediate member 35 is inserted, coincides with the outer diameter ofthe intermediate portion 13 e of the final ferrule 13, and has a portionwhose inner circumferential surface is narrowed in a tapered shapetoward the inward direction.

The cylindrical portion of the die 37 is inserted through the opening tobe the rear end portion 13 b of the ferrule 13, and the shape of theouter circumferential surface of the ferrule 13 is pressed by theportion of the die 36 where the inner circumferential surface isnarrowed in a tapered shape, thereby forming the pressed portion 13 d ofthe ferrule 13.

According to the machining method of FIGS. 8A to 8D, a pipe material issevered in the initial step to produce a workpiece (short pipe member)31 of a predetermined length, and the workpiece 31 is machined in thesubsequent step, thereby producing the ferrule 13. Therefore, it ispossible to manufacture the ferrule 13 at low cost only by a pressingprocess using a pipe material that is commercially available.

With this machining method, the front end portion 13 a of the ferrule 13for providing the seal mechanism is formed by pressing the shape withthe two dies 33 and 34 in the step of FIG. 8C, and the opening isnarrowed in the step of FIG. 8D by pressing, using the two dies 36 and37, the shape of the outer circumferential surface and the innercircumferential surface of the rear end portion 13 b for providing theholding mechanism, thereby making it possible to form the seal mechanismwith a higher precision than the holding mechanism.

The ferrule 13 of the present embodiment can also be produced by usingbulge forming. For example, rubber bulge forming may be used instead ofthe pressing process of FIG. 7D. By pressurizing and deforming a rubber,and inserting the rubber inside the short pipe member 31, it is possibleto form a portion having a greater inner diameter than the opposite endportions of the ferrule 13.

In the present embodiment, there is no particular limitation on thematerial of the fitting 10 and the pipe 95. For example, a SUS316stainless steel may be used for the fitting body 11, the nut 12 and theferrule 13 of the fitting 10, and the pipe 95. The ferrule 13 may be ofa slightly higher strength than the pipe 95. For example, acommercially-available SUS316 may be used as the pipe 95, and a materialobtained by subjecting a SUS316 to a force drawing process to increasethe strength may be used as the ferrule 13. Then, the ferrule 13 can bemade to desirably bite into the pipe 95.

The above embodiments of the present invention are illustrative of thepresent invention, and are not intended to limit the scope of thepresent invention thereto. A person of ordinary skill in the art cancarry out the present invention in various other embodiments withoutdeparting from the gist of the present invention.

FIG. 9 is a view illustrating a variation of the fitting according tothe present embodiment.

Referring to FIG. 9, a fitting 40 of the variation includes a fittingbody 41, a nut 42, and the ferrule 13.

The fitting body 41 and the nut 42 are components corresponding to thefitting body 11 and the nut 12, respectively, of FIG. 2, and arebasically the same as the fitting body 11 and the nut 12 except for whatis discussed below.

The fitting body 41 and the nut 42 have a contact portion 41 a and acontact portion 42 a, respectively, which come into contact with eachother to restrict the movement of each other when the screw couplingbetween the fitting body 41 and the nut 42 is tightened by apredetermined amount of tightening from the finger-tight state. Thepredetermined amount of tightening herein is an amount of tighteningsuch that the ferrule 13 desirably bites into the pipe 95, realizing adesirable seal mechanism and a desirable holding mechanism.

In this variation, when the screw coupling is tightened by thepredetermined amount of tightening, the fitting body 41 and the nut 42come into contact with each other so that the screw coupling can nolonger be tightened, thus suppressing over-tightening without having totighten while checking the amount of tightening by means of a mark, etc.

Note that once the fitting 40 is tightened, deformation of the pipe 95,etc., occur, thereby requiring a greater amount of tightening whenreusing the fitting 40 than in initial use. In this variation, a spacer43 having a predetermined thickness is sandwiched between the pressedportion 13 d of the ferrule and a pressing portion 42 b of the nut 42 inthe accommodation space so as to allow for additional tightening by adesired amount of tightening when reusing the fitting 40. The thicknessof the spacer 43 is such a thickness that enables desired additionaltightening. Thus, by using the spacer 43 when reusing the fitting 40, itis possible to easily enable a predetermined amount of additionaltightening.

Although one spacer 43 of a predetermined thickness is used in theexample illustrated herein, the present invention is not limited tothis. A plurality of spacers 43 may be used, and spacers 43 of differentthicknesses may be used. For example, for the second reuse (the thirduse) and thereafter, two or more spacers 43 may be sandwiched betweenthe pressed portion 13 d of the ferrule 13 and the pressing portion 42 bof the nut so as to enable a further additional tightening.Alternatively, for the second reuse (the third use) and thereafter, aspacer 43 having a greater thickness than the spacer 43 used for thefirst reuse (the second use) may be sandwiched between the pressedportion 13 d of the ferrule 13 and the pressing portion 42 b of the nut42 so as to enable a further additional tightening.

While this variation is an example that uses spacers 43 to be addedduring a reuse, the present invention is not limited to this. Anotherexample may use a spacer that is used during the first use and not usedduring a reuse. For example, a spacer of a predetermined thickness maybe placed between the contact portion 41 a of the fitting body 41 andthe contact portion 42 a of the nut 42 of FIG. 9. Then, by removing thespacer when reusing the fitting 40, it is possible to easily enable apredetermined amount of additional tightening.

FIG. 10 is a view illustrating a fitting according to another variation.

Referring to FIG. 10, a fitting 50 of this variation includes thefitting body 11, a nut 51, and the ferrule 13.

The nut 51 is a component corresponding to the nut 12 of FIG. 2, and isbasically the same as the nut 12 except for what is discussed below.

A pressing portion 52 of the nut 12 for pressing the ferrule 13 includesa depressed portion 53 and a protruding portion 54. The protrudingportion 54 is present on the outer side of the depressed portion 53 withrespect to the central axis, and the protruding portion 54 is located onthe front side of the depressed portion 53 in the axial direction.

As shown in FIG. 10A, in the finger-tight state, the depressed portion53 is in contact with the rear end portion 13 b of the ferrule 13. Asthe screw coupling between the fitting body 11 and the nut 51 istightened from this state, the depressed portion 53 presses the rear endportion 13 b of the ferrule 13, and the overall inner diameter and outerdiameter of the intermediate portion 13 e of the ferrule 13 start toincrease. However, the rear side of the intermediate portion 13 e is incontact with the protruding portion 54 above, and the increase in theouter diameter of the rear side of the intermediate portion 13 e isthereafter restricted by the protruding portion 54 present on the outerside.

Therefore, the overall outer diameter of the intermediate portion 13 ecannot be increased, and the diameter-increasing force F2 deriving fromthe force F1 from the pressing portion 52 is localized in a portion ofthe intermediate portion 13 e that is on the front side of theprotruding portion 54. As a result, as shown in FIG. 10B, the outerdiameter of the portion of the intermediate portion 13 e that is on thefront side of the protruding portion 54 increases significantly, therebyefficiently causing a rotational motion in the front end portion 13 a ofthe ferrule 13, and driving the inner circumference of the front endportion 13 a to bite into the pipe 95.

FIG. 11 is a view illustrating a fitting according to still anothervariation.

Referring to FIG. 11, a fitting 60 includes the fitting body 11, a nut61, and a ferrule 62. Although the ferrule 13 of the embodiment of FIGS.2 and 3, etc., is such that the pressed portion 13 d includes the rearend portion 13 b, the present invention is not limited to this.

In this variation, as shown in FIG. 11, a pressed portion 62 a of theferrule 62 does not include a rear end portion 62 b, and is located onthe front side of the rear end portion 62 b. Formed between the pressedportion 62 a and the rear end portion 62 b is a pipe-shaped portion 62 cof which the outer diameter and the inner diameter are equal to those ofthe rear end portion 62 b.

In the nut 61 of this variation, the smallest inner diameter of apressing portion 61 a is greater than the outer diameter of the pipe 95by such an amount that the pipe-shaped portion 62 c of the ferrule 62passes therethrough.

Also in this variation, as the screw coupling between the fitting body11 and the nut 61 is tightened, the pressing portion 61 a of the nut 61presses the pressed portion 62 a of the ferrule 62, of which the rearend portion 62 b projects on the rear side of the nut 61. The innerdiameter and the outer diameter of an intermediate portion 62 d of theferrule 62, of which the pressed portion 62 a is pressed, increase,thereby causing a rotational motion in a front end portion 62 e, anddriving the inner circumference of the front end portion 62 e to biteinto the pipe 95.

FIG. 12 is a view illustrating a fitting according to still anothervariation.

Referring to FIG. 12, a fitting 70 of this variation includes thefitting body 11, the nut 12, and a ferrule 71. The ferrule 71 is acomponent corresponding to the ferrule 13 of FIG. 2, and is basicallythe same as the ferrule 13 except for what is discussed below.

The ferrule 71 of this variation includes an intermediate portion 71 athat includes a portion that is radially non-uniformly shaped at aparticular position along the axial direction (a non-uniformly-shapedportion 71 b). In the example of FIG. 12, the non-uniformly-shapedportion 71 b included in the intermediate portion 71 a has a smallerthickness than other portions of the intermediate portion 71 a.

The non-uniformly-shaped portion 71 b is realized by a groove that iscut continuously over the entire circumference on the innercircumferential surface at a particular position of the ferrule 71 inthe axial direction. With the provision of the non-uniformly-shapedportion 71 b, the ferrule 71 of this variation can be more easilydeformed so as to increase the inner diameter and the outer diameter ofthe intermediate portion a, as compared with the ferrule 13 shown inFIGS. 2 and 3. Therefore, the tightening torque for causing a rotationalmotion in a front end portion 71 c can be suppressed to be small.

FIG. 13 is a view illustrating a fitting according to still anothervariation.

Referring to FIG. 13, a fitting 80 of this variation includes thefitting body 11, the nut 12, and a ferrule 81. The ferrule 81 is acomponent corresponding to the ferrule 13 of FIG. 2, and is basicallythe same as the ferrule 13 except for what is discussed below.

The ferrule 81 of this variation also includes a non-uniformly-shapedportion 81 b at a particular position of an intermediate portion 81 a inthe axial direction. In the example of FIG. 13, the non-uniformly-shapedportion 81 b includes a portion where the inner diameter of the innercircumferential surface is different from that of other portions and aportion where the outer diameter of the outer circumferential surface isdifferent from that of other portions. Specifically, as seen in a crosssection that includes the central axis, the inner circumferentialsurface has a depressed portion, and the outer circumferential surfacehas a projecting portion. They are the non-uniformly-shaped portion 81b, which is formed by a punching process the particular position of theferrule 81 in the axial direction from the inner circumferential surfacethereof.

With the provision of the non-uniformly-shaped portion 81 b, the ferrule81 of this variation can be more easily deformed so as to increase theinner diameter and the outer diameter of the intermediate portion a, ascompared with the ferrule 13 shown in FIGS. 2 and 3. Therefore, thetightening torque for causing a rotational motion in a front end portion81 c can be suppressed to be small.

Note that although this variation is directed to an example where theferrule 81 is punched from the inner circumferential surface thereof,the present invention is not limited to this, and thenon-uniformly-shaped portion may be formed by punching from the outercircumferential surface.

Although the non-uniformly-shaped portion 81 b is formed by a punchingprocess in the example illustrated herein, the present invention is notlimited to this. As another example, the non-uniformly-shaped portion 81b may be formed by a cutting process.

The non-uniformly-shaped portion 81 b extending over the entirecircumference of the ferrule 81 of this variation does not need to beformed by a single iteration of a punching process, but may be formed bya plurality of separate iterations of a punching process.

FIGS. 14A and 14B are views illustrating a fitting according to stillanother variation.

Referring to FIG. 14A, a fitting 100 includes a fitting body 101, a nut102, and a ferrule 103. The ferrule 103 includes a rising portion 103 a,an intermediate portion 103 b, and a pressed portion 103 c. Note thatalthough the boundary between the intermediate portion 103 b and thepressed portion 103 c is indicated by a broken line in the figure, thisbroken line does not indicate a position that strictly separates theintermediate portion 103 b and the pressed portion 103 c from eachother. This broken line is drawn for the purpose of illustration so thatthe function of the intermediate portion 103 b and that of the pressedportion 103 b can be easily discussed in the present specification.

In this variation, there is a first clearance space on the left of therising portion 103, but there is no second clearance space on the outerside of the intermediate portion 103 b. The rising portion 103 aincludes a portion (a non-uniformly-shaped portion) near theintermediate portion 103 b where the inner circumferential surface isdepressed and the thickness is smaller than other portions of theintermediate portion 103 b.

As the screw coupling between the fitting body 101 and the nut 102 istightened from the finger-tight state, a pressing portion 102 a of thenut 102 presses the pressed portion 103 c of the ferrule 103 in theaxial direction as shown in FIG. 14B. The rising portion 103 a of theferrule 103 is pressed in the axial direction and rises due todeformation of primarily the portion thereof having a smaller thickness.In this process, the outer diameter of the intermediate portion 103 bdoes not hardly increase. As the rising portion 103 a rises, arotational motion occurs in a front end portion 103 d of the ferrule103, and the inner circumference is driven to bite into the outercircumferential surface of the pipe 95 based on the principle ofleverage, with the outer circumference of the front end portion 103 d asthe fulcrum and the inner circumference as the point of load.

Thus, it is possible to cause a rotational motion in the front endportion 103 d and drive the inner circumference to bite into the outercircumferential surface of the pipe 95 based on the principle ofleverage, as long as there is a first clearance space 105 a on the outerside of the rising portion 103 a for allowing the rising portion 103 ato rise, even if there is no second clearance space on the outer side ofthe intermediate portion 103 b of the ferrule 103, in the finger-tightstate.

Note that although this variation is directed to an example where thesurface of the pressed portion 103 c of the ferrule 103 and the surfaceof the pressing portion 102 a of the nut 102 to be in contact with eachother are both a flat surface perpendicular to the central axis, thepresent invention is not limited to this example. As another example,those surfaces do not need to be perpendicular to the central axis.Moreover, those surfaces do not need to be flat surfaces. For example,there may be a depressed portion in the pressed portion 103 c of theferrule 103, while there is a protruding portion at a position of thepressing portion 102 a of the nut 102 corresponding to the depressedportion. Alternatively, the pressed portion 103 c of the ferrule 103 maybe a flat surface, while there is a protruding portion in the pressingportion 102 a of the nut 102.

Although this variation is directed to an example where the risingportion 103 a of the ferrule 103 is provided with a portion of a smallerthickness therein so as to make it easier for a rotational motion tooccur in the front end portion 103 d, the present invention is notlimited to this example. With the first clearance space, even if theferrule 103 has a uniform thickness, the rising portion 103 rises whenpressed by the nut 102 in the axial direction, thereby causing arotational motion in the front end portion 103 d.

Moreover, in this variation, the thickness of the intermediate portion103 b of the ferrule 103 is set to be greater than the rising portion103 a so as to prevent the outer diameter of the intermediate portion103 b from increasing when pressed by the nut 102 in the axialdirection. However, the present invention is not limited to thisexample. As another example, the ceiling formed by the innercircumference of the nut 102 may prevent the outer diameter of theintermediate portion 103 b of the ferrule 103 from increasing. In such acase, the ceiling may from a cylindrical inner circumferential surface,and one or more annular protruding portions may be provided at aposition on the inner circumference of the nut 102 corresponding to theintermediate portion 103 b of the ferrule 103 so as to prevent the outerdiameter of the intermediate portion 103 b from increasing.

Although the embodiment of FIGS. 2 and 3 is directed to an example wherethe pressing portion 12 a forms an acute angle with the outercircumferential surface of the pipe 95 along a cross section thatincludes the central axis, the present invention is not limited to this.As another example, the pressing portion 12 a may be perpendicular tothe outer circumferential surface of the pipe 95. If the pressingportion 12 a of the nut 12 is perpendicular, a force is efficientlyapplied on the pressed portion 13 d of the ferrule 13 in the axialdirection, thereby also making it easier to generate a force derivingtherefrom that increases the inner diameter and the outer diameter ofthe intermediate portion 13 e of the ferrule 13. As a result, it iseasier for a rotational motion to occur in the front end portion 13 a ofthe ferrule 13.

Although the embodiment of FIGS. 2 and 3 is directed to an example wherethe nut 12 presses the pressed portion 13 d of the ferrule 13 in theaxial direction, and the fitting body 11 and the front end portion 13 aof the ferrule 13 come into contact with each other, thereby making therising portion 13 c of the ferrule 13 rise toward the tapered innercircumferential surface 11 a of the fitting body 11, the presentinvention is not limited to this example. As another example, the risingportion 13 c and the pressed portion 13 d of the ferrule 13 may beprovided in reversed positions. In such a case, the nut 12 includes atapered inner circumferential surface, similar to the tapered innercircumferential surface 11 a of the fitting body 11 of FIG. 2, to be incontact with the front end portion 13 of the ferrule 13. As the nut 12presses, with its tapered inner circumferential surface, the risingportion 13 c in the axial direction, the fitting body 11 in contact withthe pressed portion 13 d of the ferrule 13 relatively pushes back thepressed portion 13 d. This deforms the ferrule 13, causing a rotationalmotion in the front end portion in contact with the nut 12, so that theinner circumference is driven to bite into the outer circumference ofthe pipe 95 based on the principle of leverage, with the outercircumference of the front end portion serving as the fulcrum and theinner circumference as the point of load.

While the present invention has been described above with reference toembodiments and variations, the present invention is not limited to theembodiments and variations. Various changes that can be appreciated by aperson of ordinary skill in the art can be made, within the scope of theinvention, to the configuration and the details of the present inventionas defined in the claims.

This application claims priority based on Japanese Patent ApplicationNo. 2012-169271 filed on Jul. 31, 2012, the content of which is hereinincorporated by reference in its entirety.

What is claimed is:
 1. A ferrule manufacturing method for manufacturinga ferrule for use in a fitting to be connected to a pipe, the methodcomprising: a first step of producing an intermediate pipe member havinga predetermined length, the intermediate pipe member having a uniformouter diameter and a uniform inner diameter between opposite endsthereof; and a second step of machining the intermediate pipe member toproduce the ferrule including a first end portion, a second end portion,a great-diameter portion between the first end portion and the secondend portion, and a through hole extending from the first end portion tothe second end portion for receiving the pipe, the great-diameterportion having a greater inner diameter than the first end portion andthe second end portion between the first end portion and the second endportion, and the first end portion and the second end portion bothhaving such a first inner diameter that the pipe can be accommodatedtherein, wherein: a rising portion of the ferrule produced by themachining includes the first end portion, a pressed portion locatedcloser to the second end portion than the rising portion, and anintermediate portion including the great-diameter portion, theintermediate portion connecting together the rising portion and thepressed portion, wherein the rising portion is inwardly tapered, thepressed portion is inwardly tapered, and the intermediate portion iscylindrical; the ferrule is used in the fitting including: a firstmember having a through hole constructed and arranged to receive thepipe, the first member including a first tapered inner circumferentialsurface having a tapered shape, constructed and arranged to be incontact with the first end portion of the ferrule; a second memberhaving a through hole constructed and arranged to receive the pipe, thesecond member being coupled by screw coupling with the first member,with a central axis of the through hole being aligned with a centralaxis of the through hole of the first member; the second memberincluding a pressing portion for pressing at least a portion of thepressed portion of the ferrule and for deforming the ferrule to increasean outer diameter of the intermediate portion; and an accommodationspace in which the ferrule is placed formed by an inner circumferentialsurface of the first member, an inner circumferential surface of thesecond member and an outer circumferential surface of the pipe, with acentral axis of the through hole being aligned with the central axes ofthe first member and the second member, the accommodation spaceincluding a first clearance space constructed and arranged toaccommodate the ferrule therein and to allow the rising portion to riseso as to increase an angle of the rising portion with respect to theouter circumferential surface of the pipe; and as the screw couplingbetween the first member and the second member is tightened, the risingportion of the ferrule rises, by the increasing of the outer diameter ofthe intermediate portion, with an outer circumference of the first endportion serving as a fulcrum of the principle of leverage and an innercircumference of the first end portion serving as a point of load of theprinciple of leverage, causing the inner circumference of the first endportion to rotate to be driven to bite into an outer circumference ofthe pipe.